The adsorption of various alkylammonium cations from aqueous solution by sodium and calcium montmorillonite has been studied. Adsorption occurred through an exchange reaction between the inorganic cations on the clay and the alkylammonium ions in solution. The affinity of the clay for these cations was linearly related to molecular weight, with the exception of the smaller methyl-ammonium and the larger quaternary ammonium ions. Comparison of primary, secondary and tertiary amines containing the same alkyl groups showed that the affinity of the clay was greatest for the primary amine and least for the tertiary. This behaviour has been interpreted in terms of the size and shape of the cations. X-ray diffraction analysis showed that no more than a single layer of adsorbed cations was present in the inter-lamellar space at maximum adsorption. Comparison between Δ-values and the thickness of the adsorbed ions showed that there was a contraction in the apparent contact distance of these cations. The amount of contraction could be accounted for by ‘keying’ of the adsorbed ions into the montmorillonite surface.

The chemisorption of methylene blue by kaolinite crystals increased as the aqueous suspensions changed from acid to alkaline because, at high pH values, not only the basal pinacoids but the edge-faces were negatively charged. The inability to calculate acceptable specific surfaces or cation exchange capacities from the chemisorption data is discussed, with special reference to the orientation of adsorbed dye cations, the covering of more than one exchange site by a monomer or polymer, the different concentrations of exchange sites on the basal pinacoids and edge-faces respectively, the possibility that such sites occur on the tetrahedral rather than on the octahedral basal pinacoid, and the incomplete replacement of inorganic cations.

Using the adiabatic calorimeter which has been developed by Nagasaki & Takagi (1948) and manufactured by the Rigaku Denki Company, the energy changes associated with the dehydration and dehydroxylation processes of clay minerals were measured at room pressure. The samples studied were mont-morillonite, chlorite (trioctahedral type), and three kinds of interstratified minerals with component layers such as mica, dioctahedral chlorite, and montmorillonite. ΔH-values due to the dehydration of the interlayer region were 9·8 kcal/H2O mole for montmorillonite and 12·4–13·4 kcal/H2O mole for interstratified minerals mica-montmoriIlonite and dioctahedral chlorite-montmorillonite. The values due to dehydroxylation of the silicate layer were 17·7 kcal/H2O mole for montmorillonite, 16·8–17·5 kcal/H2O mole for the interstratified mica- montmorillonite, and 19·3 kcal/H2O mole for chlorite. The value for the dehydroxylation of the hydroxyl layer of chlorite was 19·3 kcal/H2O mole. For the sake of comparison, the heat of transition α↔β of quartz was found to be 140 cal/mole. The reproducibility of these values was in the range of ±5%.

A 2–20 µ fraction of phlogopite has been converted to the sodium form by use of sodium tetraphenylboron-NaCl solutions. The cation exchange capacity of the treated material increases to a maximum of about 212 m-eq/100 g, which agrees well with the K2O + Na2O content of the initial mineral. Li-, Na-, Ca-, and Mg-saturated forms have been prepared and examined by X-ray diffraction and by thernogravimetric measurements in air, in vacuo, and at progressively elevated temperatures. Hydration states corresponding to double water layers are observed for the Mg- and Ca- forms, and to single water layers for the Mg-, Ca-, Na-, and Li- forms. The numbers of water molecules per unit cell and per interlayer cation are considered for the various hydration states.

The OH-OD exchange of kaolin minerals through contact with D2O introduced into interlayer space via intersalation resulted in a partial shift of the OH absorption bands. The total decrease in OH absorbance upon deuteralion was 52, 56, and 47% for the kaolinite, dickite-nacrite, and halloysite respectively, but the percentage decrease differed for the different absorption maxima of any one mineral. A secondary OH—OD exchange in the deuterated specimens was also observed upon heating to 350 and 400° C. These data together with the lack of deuteration in montmorillonite, and available orientation data on the kaolin OH groups by infrared spectroscopy, suggest that only two-thirds of the inner-surface OH groups form the interlayer OH—O bonds.

A mixed-layer clay mineral from a Permian sandstone at Maitland, New South Wales has been identified as 2:1 mica-montmorillonite structure with ‘imperfectly regular’ interstratification. The results from Fourier transform analysis and Fourier synthesis of 00l X-ray diffraction data have not fully elucidated the interlayering patterns but have indicated that there is complete alteration in the stacking and that the 1:1 (allevardite type) layer sequence relationship is strongly developed.

X-ray diffraction, differential thermal, thermogravimetric, chemical, cation exchange and electron microscopic data for the mineral are given. The chemical analysis for the Na+-saturated material gives the structural formula

K0.90 Ca0.06 Na0.49 [Al3.52, Fe0.183+ Mg0.27 Ti0.03 (Al1.24 Si6.76) O20 (OH)4] H2O

It is considered that most of the fixed K+ and Ca++ ions are probably held in the mica interlayers, while the exchangeable components are largely accommodated in the expanded montmorillonite zones.

In the quantitative X-ray diffraction analysis of a series of samples, the problems arising from the variable compositions and degrees of crystallinity of clay minerals were overcome to a great extent by the use of standards extracted from the samples. Procedures are given for separation of the montmorillonite standard by differential settling of Na-montmorillonite solvated in an ethanol solution and for isolation of the kaolinite, mica, and chlorite standards by density separation of their Na-forms in thallous formate.

Calibration curves were prepared from the X-ray diffractograms obtained for series of known mixtures of Ca-forms of the standards and the internal standard boehmite using both powder and smear-oriented mounting techniques.

Three soils of the Strathdon area, Aberdeenshire, derived from a biotite-rich quartz-gabbro and representing well-drained, imperfectly drained and poorly drained types, were studied. The 50–200 µ fractions contained mainly plagioclase feldspar, amphibole (tremolite and hornblende), biotite and quartz and the following order of relative stability was established: quartz > amphibole > plagioclase feldspar > biotite. In all soils biotite was found to weather to a 14 Å aluminous vermiculite-chlorite with zones of kaolinite. The clay mineral composition of three soils was identical, consisting of trioctahedral vermiculite-chlorite, trioctahedral illite, kaolinite and gibbsite. These minerals originated in various ways through the decomposition of biotite which thus plays a key role in the origin of the clay fraction. It is suggested that the clay mineral constituents of the soils were formed in a regolith predating the last glacial period, and that post glacial soil-forming processes have modified them only slightly.

The alteration products of five sub-marine tuffs from the Mount Carmel were analysed chemically, by X-ray, D.T.A. and I.T.A. techniques and their mineralogical composition determined. Smectites are dominant in all the samples. In the less altered tuffs the smectite seems to consist of a mixture of saponite with a smectite from the beidellite-nontronite series. In the more intensely altered tuffs the saponite disappears and a swelling chlorite appears. The formation of the swelling chlorite is attributed to the degradation of the saponite. These mineralogical changes are accompanied by the loss of a large part of the alkali and alkaline earth cations.